Water-soluble polymeric films are commonly used as packaging materials to simplify dispersing, pouring, dissolving and dosing of a material to be delivered. For example, packets made from water-soluble film are commonly used to package household care compositions, e.g., a pouch containing a laundry or dish detergent. A consumer can directly add the pouch to a mixing vessel, such as a bucket, sink or washing machine. Advantageously, this provides for accurate dosing while eliminating the need for the consumer to measure the composition. The pouch may also reduce mess that would be associated with dispensing a similar composition from a vessel, such as pouring a liquid laundry detergent from a bottle. The pouch also insulates the composition therein from contact with the user's hands. In sum, soluble polymeric film packets containing pre-measured agents provide for convenience of consumer use in a variety of applications.
Some water-soluble polymeric films that are used to make packets will incompletely dissolve during a wash cycle, leaving film residue on items within the wash. Such problems may particularly arise when the pouch is used under stressed wash conditions, such as when the pouch is used in cold water (e.g., water as low as 5° C. and/or up to 10° C. or 15° C.), in a short wash cycle, and/or in a low-water wash cycle (e.g., wash liquors from about 3 L to about 20 L). Notably, environmental concerns and energy cost are driving consumer desire for utilizing colder wash water and shorter wash cycles.
The formation of water-soluble single unit dose (SUD) pouches includes attachment of at least an upper layer of water soluble film to a lower layer of water-soluble film. In the case of a multi-compartment pouch, it is sometimes desirable to have one pouch compartment separated from a second pouch compartment by a middle layer of water-soluble film, i.e. in so-called superposed multi-compartment pouches. In such a superposed multi-compartment pouch there is a seal between the top film and the middle film, and between the middle film and the bottom film. In another embodiment of a multi-compartment pouch, two pouch compartments are positioned side-by-side, for example including two layers of water-soluble film which are sealed in a middle region between pouch compartments. In such side-by-side pouches, a good seal quality between adjacent compartments is desired to prevent liquid migration from one compartment to the other through the seal. Such pouches known in the art do not have seals as strong as desired. While it is possible to create a strong seal by heat sealing the layers together, this can lead to problems such as weakness at the edge of the heat seal and leaking pouches. Additionally, heat sealing may induce additional crystallinity, resulting in seals that may be less soluble than a corresponding seal produced by solution sealing.
There remains a need for water-soluble films and related packets having the desired characteristics of good water solubility (e.g., cold water solubility), chemical resistance, chemical and physical compatibility with laundry actives, other detergent actives, or other compositions in contact with the film or pouch formed therefrom, and desirable mechanical properties including strong seals, high tensile strength, and good processability. Once formed, whether as a film or a composition-containing pouch formed therefrom, supply chain considerations can result in a substantial passage of time (e.g., at normal or elevated temperatures) before utilization of the end product. Accordingly, there is further a need for improved mechanical properties (e.g., seal strength, tensile strength) after such passage of time and change in film properties.